1. Field of the Invention
The present invention relates to a torsion damping device, especially for a friction disc clutch for an automotive vehicle, comprising at least three coaxial parts mounted in pairs and rotatable with respect to each other within the limits of a predetermined angular displacement and against the biassing action of resilient means, the coaxial parts comprising a first part including a hub, a second part comprising a main damper plate with relative rotational displacement means between it and the hub, and a third part comprising at least one rotatable element which constitutes transversely an annular member surrounding the hub but not coupled with the latter.
2. Description of the Related Art
Such a torsion damping device is described for example in French Patent Application No. 2 560 329 and in French Patent Application No. 2 573 830.
In those constructions there is interposed radially, between the rotatable element (which is commonly referred to as a guide ring) and the hub, a ring member having an internal portion for engagement with the hub, and an external portion for engagement with the rotatable element.
It has already been proposed, for instance, in French Patent Application No. 2 496 786, to provide this ring member with the ability to deform radially so as to avoid parasitic frictional effects which would be capable of masking the action of resilient means of low stiffness.
Such an arrangement allows vibrations to be satisfactorily filtered during the slow running mode, but when in the normal running mode, in which the transmitted torque is not negligible, this solution leads to disadvantages.
In particular, in respect of a damper plate having a facility for relative movement with respect to the hub, this leads to increased wear in the components of the torsion damper, by reason especially of the elasticity of the ring member and of the radial forces which appear during normal running. These wear effects have an effect on the length of life of the clutch.
An object of the present invention is to reduce these disadvantages and thus to provide a ring member capable of minimising wear, while also being radially deformable resiliently so as not to mask the action of resilient means of low stiffness.